Cultures prepared from the dissociated Peyer's patches of normal rabbits respond to sheep erythrocytes. The response is comparable to that obtained with spleen cultures from the same animals and is not dependent on the presence of the epithelial cells which line the lumen. Similar thymic cultures do not respond.

Our experiments with cultures prepared from rabbits which have received one or two injections of SRC show that the Peyer's patches contain both IgM and IgG "memory" cells which have migrated from the spleen. The concentration of these cells in the spleen remains several hundredfold higher.